The invention belongs to the technical field of wireless communications, and relates to a multi-mode resonator and a filter thereof. The multi-mode resonator includes an annular transmission line, a first open-circuit transmission line, a second open-circuit transmission line, a third open-circuit transmission line, a fourth open-circuit transmission line and a fifth open-circuit transmission line. The open-circuit transmission lines are mounted on the annular transmission line in symmetry, and the fourth and fifth open-circuit transmission lines are coupled with the annular transmission line. In the filter, a pair of T-shaped filter feeder lines are added to the multi-mode resonator. According to the invention, the multi-mode resonator and the filter thereof have the characteristics of high selectivity, small area and flexible dual-band relative position adjustment.